1. Field of the Invention
This invention generally relates to wireless communications and, more particularly, to a system and method for automatically reestablishing a communication in a rendezvous scheduled network such as Bluetooth scatternets.
2. Description of the Related Art
FIG. 1 illustrates conventional Bluetooth piconet communication patterns (prior art). In Bluetooth, and similar communication systems, a master/slave relationship is used to control access of the communication channel. Communication occurs only between device pairs where one device is the master and the other is slave. The slave is required to listen for the master in all master-to-slave slots. The slave is only allowed to transmit to the master when it receives a packet addressed to it from the master. In this case the slave is allow to transmit to the master in the following slave-to-master slot. The master is free to communicate with any slave in any master-to-slave slots. A piconet is a group of devices comprised of one master and from one to seven slaves.
FIG. 2 illustrates a conventional Bluetooth scatternet communication pattern (prior art). In Bluetooth, a scatternet is created when at least one device is active in more than one piconet. The device that is present in more than one piconet must share its communication capacity between piconets. This device is known as a PMP (Participant in Multiple Piconets). The PMP may be a slave in multiple piconets, or a master in one piconet and a slave in one or more other piconets. If the device has multiple piconet connections, the previous rules used to control communication cannot be used because of conflicting requirements. It is not possible for a slave to listen in all master-to-slave slots. Because of this rule, a higher-level scheduler is needed to manage the orderly exchange of communication to PMPs.
FIG. 3 is a diagram illustrating pseudorandom time points (prior art). One higher level scheduling method used to manage communication in a scatternet is called pseudorandom scheduling. Pseudorandom scheduling uses a system that consists of time points (TP) that define the initiation of a communication period. A communication period starts at the TP and typically continues until terminated by another TP for another communication link. The communication period defines a time period where there is continuous data exchange between a device pair. The termination of the communication period typically occurs because another TP occurs on another link, which starts a communication period on that link. The location (in time) of the initiation TP is determined by a pseudorandom generator. Both devices on the communication link are able to determine the position of the TPs and initiate communication when they occur. Each communication link has a unique and random sequence of TPs. A pseudorandom position of time points is used to avoid any systematic collisions, allocating communication capacity throughout the scatternet in a fair way.
Additional details of a Pseudorandom scheduling method are provided in pending invention PSEUDO-RANDOM DYNAMIC SCHEDULER FOR SCHEDULING COMMUNICATION PERIODS BETWEEN ELECTRONIC DEVICES, invented by Daryl Hlasny, Ser. No. 10/006,440, filed Nov. 20, 2001, which is incorporated herein by reference.
In a system that uses pseudorandom scheduling of communication periods, the full duration of the communication period is not used when no data is available for exchange. The communication capacity of the communication period is wasted in this case. It is then highly desirable to use this capacity for communication on another link where there is data to be transmitted. Furthermore, it is highly desirable to distribute this unused capacity in a fair way between the links where it can be used to maintain the fair distribution of capacity in the system. More specifically, when a communication period is very short, as is the case when only polling occurs during the communication period, it is desirable if the remaining unused time in the communication period is used effectively.
It would be advantageous if latency in a pseudorandom scheduled communication network could be reduced.
It would be advantageous if the efficiency of a pseudorandom scheduled communication system could be improved.
It would be advantageous if the fairness of scheduling in a pseudorandom communication system could be maintained, while reducing latency and improving efficiency.
It would be advantageous if unfinished communications could automatically by continued in time slots where the communicating pair have no information to transfer.